The role of the sympathetic nerves and humoral factors such as peptides and amines in regulating the pulmonary vascular bed will be investigated in a variety of animal species. The effects of stimulation of the sympathetic nerves and infusion of vasoactive substances will be evaluated. Right heart and transseptal catheterization techniques will be utilized to control a variety of variables in the intact spontaneously breathing animal. Studies of the morphology and ultrastructure of the innervation of the pulmonary vascular bed will be undertaken using both the light and electron microscopes. The effects of hypoxia, hypercapnia, and atelectasis will be studied. The effects of inhibition of prostaglandin synthesis on the pulmonary vascular bed and on the airways will be evaluated in the dog. The interactions between prostaglandins and the sympathetic nervous system will be assessed in the hindlimb, renal and mesenteric vascular beds. The effects of inhibition of prostaglandin synthesis on responses to adrenergic stimuli will be studied in the peripheral vascular bed. The effects of prostaglandins and of synthesis inhibitors on the venous system will be studied.